If the new job is one you REALLY want and believe you'll enjoy, I personally would do whatever it takes to get that job. Personally I rate getting a job that really floats your boat way above a pay off. If you work a notice period before starting the new one, you're not actually "losing" anything, it's money you've never received, so you can't lose it.
If, however, the new role is "just another job" and you just want out of the current one much more than you want into the new one, do your best to get the redundancy cash and then jump over.
https://www.gov.uk/redundant-your-rights/overview